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Regarding its wide range of applications in different industries, such as oil and gas, and for manufacturing equipment used to control pollution and recycle industrial wastes, Inconel 686 turning process is highly important. The alloy is highly resistant to high temperatures and corrosion, and thus it can preserve its properties at high temperatures. Due to its low heat transfer coefficient and work hardening during operation, Inconel 686 is considered a difficult‐to‐cut material, and hence, turning Inconel 686 is challenged with major limitations regarding input parameter level and cutting fluid and issues such as reduced surface quality. The input parameter level and cutting fluid limitations might severely harm the environment and humans, decrease the machining efficiency and keep cleaner production goals out of reach. Novel cooling methods such as cryo‐MQL can contribute to achieving cleaner production goals. Cooling methods improve the machining performance and prohibit any damage to the surface integrity. In this study, cryo‐MQL, along with carbide‐coated tools and biodegradable vegetable oil, was adopted. The efficiency and success rate of cryo‐MQL were evaluated by comparing the results with those of MQL and wet methods. A wide range of output parameters, such as residual stresses, cutting zone temperature, cutting forces, tool wear, surface smoothness, surface defects and micro‐hardness, were assessed by changing the cutting speed and feed rate. The results indicated that cryo‐MQL could reduce the cutting forces, tool wear rate, cutting zone temperature and residual stresses while improving the surface quality. Moreover, environmental concerns were completely dealt with. Due to the increased possibility of higher input parameter levels, the time and cost of the cutting process were significantly reduced. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate how weld overlays with nickel superalloys are important for the integrity, due the high temperatures and corrosive environments that can be experienced in mineral processing environments, of mining and processing equipment. The Ni-Cr-Mo superalloy Inconel 686 overlays are fabricated through automatic gas metal arc welding with variations in arc voltage and travel speed (i.e., heat input), and they have overlap between adjacent weld tracks for applications in the mining and minerals sector. The impact of variations in the process parameters and the size of the weld overlapping on the dilution, solidification morphology, microsegregation, and microhardness were investigated. Both geometric and chemical composition definitions were used to quantify the extent of the weld dilution. Subsequently, the weld geometry and dilution were correlated with the solidification microstructure and phase transformations. The maximum dilutions were measured to be 13.63% (1/2 overlap, 5.96 kJ·cm−1) and 15.39% (1/3 overlap, 4.77 kJ·cm−1), which shows that less of an overlap increases the dilution level. Scanning electron microscopy and chemical composition analysis revealed that an increase in weld heat input and dilution level led to higher levels of microsegregation for Mo and Cr, as well as the volume fraction of Mo- and Cr-rich phases in the interdendritic/intercellular regions in the overlay layer. Analysis of the weld overlays in the current study revealed strong and unprecedented connections between the weld overlay process conditions, the resultant metallurgy (i.e., dendrite arm spacing, microsegregation, and phase formation), and the hardness of the overlay. It was concluded that the optimal weld overlays in the processing window studied in this investigation were fabricated at mid-level heat inputs (i.e., 4–5 kJ·cm−1) and a 1/2 track overlap. [ABSTRACT FROM AUTHOR]

Weld overlays of Ni-based superalloys provide high-temperature corrosion, oxidation, and wear resistance for industrial applications. The objective of this study was to evaluate the microstructure of Ni–Cr-Mo superalloy Inconel 686 overlays fabricated using automatic gas metal arc welding (GMAW) with three different levels of voltage, travel speed, and wire feed speed. The variation of these parameters and their effects on the weld quality, dilution, and microsegregation were analyzed. The weld surface quality was assessed by visual examination. The weld dilution was measured by both geometric and chemical composition definitions. The maximum dilution was measured at 13.63%, induced by the highest weld heat input (5.97 kJ cm−1) and lowest wire feed speed (6 m min−1). The overlay dilution and the heat-affected zone (HAZ) size decreased by increasing the wire feed speed. However, increasing the wire feed speed and the heat input reduced the weld quality and even resulted in noncomplete joints. Microsegregation of elements was evaluated using energy-dispersive X-ray spectroscopy (EDS) analysis and it was found that microsegregation of Mo and Cr and the volume fraction of secondary phases in the interdendritic areas increased with increasing the weld heat input. According to the visual examination results and macro- and microscopic evaluation, the weld overlay parameters were found to be optimized for the mid-level heat inputs (4–5 kJ cm−1) and wire feed speeds between 6 and 8 m min−1. [ABSTRACT FROM AUTHOR]

The This analysis represents the optimization process for materials removal rate (MRR), tool wear rate (TWR), and surface roughness (Ra) of die-sinking EDM on Inconel 686 material by using response surface methodology (RSM). Inconel 686 is an advanced corrosion resistance alloy that resists oxidization in mixed acid environments and other harmful effects of high-temperature exposure. High conductive aluminum (99.99% aluminum) Inconel 686 material is taken as a workpiece for conducting the experiments. Four controllable input parameters: spark current, pulse on time, % duty cycle, and voltage have been considered process parameters. The investigation is based on an experimental design using design expert software in which central composite design (CCD) of response surface methodology is used. A total of 30 tests have been conducted for various combinations of process factors. Multiple influences of process factors and their function relations on characteristics responses are examined using analysis of variance (ANOVA). Spark current, pulse on time, duty cycle, and voltage significantly affect the MRR, TWR, and Ra. The model adequacy has very satisfactory for MRR, TWR, and Ra. The importance is 0.9222, 0.9402, and 0.8764 for MRR, TWR, and Ra. The values of adequate precision are 13.5486, 14.7249, and 12.9433 for output characteristics MRR, TWR, and Ra. [ABSTRACT FROM AUTHOR]

The 13CrMo4-5 ferritic steel is commonly used in power plants, due to its favorable mechanical properties. According to EN10028-2, this steel can be used at temperatures up to 570 °C because of its creep behavior. The inefficient corrosion resistance limits the application of this steel to lower temperatures depending on the gas temperature and slag formation. Therefore, the application of a highly resistant Ni-based coating is proposed to extend the corrosion resistance of elements made of ferritic steel. The corrosion test was performed in an environment containing a mixture of gases, like O2, COx, and SOx, and deposited ashes with elements, e.g., Na, Cl, Ca, Si, C, Fe, and Al. The exposure time was, respectively, 240 h, 1000 h and 4500 h at a temperature of 600 °C. The oxide scale formed on the 13CrMo4-5 steel was significantly thicker than on the IN686 coating. The microstructure and chemical and phase compositions of the oxide scale were investigated using light optical microscopy together with scanning and transmission electron microscopy techniques. Energy dispersive x-ray analyses were preformed when appropriate. [ABSTRACT FROM AUTHOR]

Dilution is an event that has a great influence on the microstructure and, consequently, in the properties of weld claddings. The present study evaluated the effect of dilution level on the microstructure of the fusion zone of alloy Inconel 686 weld claddings. The claddings were welded by the TIG cold wire feed process. The dilution was calculated from the geometric characteristics and based on chemical composition of the materials obtained by energy dispersive X-ray spectroscopy and optical emission spectroscopy. The microstructures of all claddings were composed by a ?-FCC matrix with some minor precipitates. These particles are called in the literature topologically close-packed phases (TCP). These precipitates assumed several morphological aspects, being the shapeless morphology observed in more frequency in all claddings evaluated, independent of dilution level. A phase with lamellar morphology, with growth establishing an orientation relationship with the ?-FCC matrix solidification direction, was observed only in claddings with a low dilution level. In addition, a shapeless phase with a fine precipitation aggregated was observed in claddings with a high dilution level. [ABSTRACT FROM AUTHOR]

The article presents the investigation results of microstructural, chemical composition changes after clad layers of Inconel 625 and Inconel 686 alloys weld overlaid on boiler tubes. The boiler tubes made of 16Mo3 steel were cladded in the Boiler Factory SEFAKO S.A. using CMT technique. The microstructure and chemical composition of coatings were analysed using light microscopy, scanning and transmission electron microscopy. The value of the partition coefficient k was determined for Inconel 625 and Inconel 686 clad layers. The value was calculated by dividing the average content (% wt.) of Ni, Cr, Mo, Fe, Nb and W. [ABSTRACT FROM AUTHOR]

Quantitative analyses produce important information concerning the microstructural characteristics of materials, which are reflected in the main properties of the materials. The secondary and backscattered electron modes represent the two main techniques most used in scanning electron microscopy, to produce images and, consequently, realize a quantitative analysis. However, each technique has its advantages and problems. The present work proposed evaluate what is the best SEM technique to quantify secondary phases in a cladding of Inconel 686, which can be extended to the other classes of nickel based alloys rich in Mo. It was performed a quantitative analysis of several images to characterize the microstructure of Inconel 686 weld cladding. The images were obtained using three modes: secondary electron (SE), Z contrast backscattered electron (BSE) and topographic backscattered electron (BSE). The segmentation and quantify of secondary phases was performed by SVRNA software. The statistical results revealed differences between the techniques. The secondary electron mode included several artefacts that reduced the precision of the quantification study. The BSE modes are shown to be the best techniques for quantification. [ABSTRACT FROM AUTHOR]

Weld overlay with Ni-based superalloys is an important option for industrial applications. New alloys have been developed to assure desirable characteristics such as corrosion resistance. The Inconel 686 superalloy was developed with a higher Cr and Mo content in order to improve its resistance to corrosion. However, information in the literature about the solidification and weld microstructure of this alloy is very limited. This work, which presents important results concerning the microstructure of the Inconel 686 superalloy, focuses on a detailed analysis of the secondary phases formed during solidification using transmission electron microscopy. The results show that there are several Mo-rich precipitates of the P-phase type in the matrix, and the σ-phase and μ-phase in minor amounts. [ABSTRACT FROM AUTHOR]